Pertussis: New preventive strategies for an old disease.

In the last twenty years, despite high vaccination coverage, epidemics of pertussis are occurring in both developing and developed countries. Many reasons could explain the pertussis resurgence: the increasing awareness of the disease, the availability of new diagnostic tests with higher sensitivity, the emergence of new Bordetella pertussis (B. pertussis) strains different from those contained in the current vaccines, the asymptomatic transmission of B. pertussis in adolescents and adults and the shorter duration of protection given by the acellular pertussis (aP) vaccine. New preventive strategies have already been implemented, such as booster doses of aP vaccine in adolescents and adults, maternal immunisation during pregnancy and the "cocooning" strategy, but more are still needed. Knowing what is new about this old disease is necessary to reduce its incidence and to protect infants too young to be vaccinated, which have the highest risk of complications and death.

A cross-sectional study of Bordetella pertussis seroprevalence and estimated duration of vaccine protection against pertussis in St. Petersburg, Russia.

BACKGROUND: In Russia as in other countries introduction of infant vaccination against pertussis in 1950s led to dramatic decrease of whooping cough. The current vaccination schedule includes a 3-dose infant series and toddler booster; the pre-school booster was cancelled in 1980s and never reintroduced. Whole-cell vaccines, and in a smaller proportion acellular vaccines are used for all doses. However, pertussis incidence in urban settings is high with highest burden in school children. We conducted a study of seroprevalence of recent pertussis infection to estimate the duration of protection from the 4-dose series. MATERIALS AND METHODS: Sera sample from 395 St Petersburg children aged ≥3 years and <14 years were tested for pertussis toxin antibodies using a commercial PT ELISA test. Only children with completed 4-dose vaccination course were included in the study. Age-specific seroprevalence of recent pertussis infection was analyzed for trends. RESULTS: Children fully vaccinated against pertussis at 3 years old had significant delays in infant vaccination schedule: only 83.5% received at least one dose of pertussis vaccine at 6 months of age and 25.6% received their toddler booster before 24 months-old. Overall, 10.6% of children demonstrated the serological signs of the infection in the last 12 months. A clear trend (r2 = 0.692) of increasing proportion of infection in the last 12 months was observed in children who had received their last dose of vaccine 6 years and more prior to the study. CONCLUSION: Our study demonstrates that Russian children become susceptible to infection at or soon after entering school. The results confirm the waning of vaccine-elicited immunity around school-age and support the need for a booster dose at that age.

Bordetella pertussis population dynamics and phylogeny in Japan after adoption of acellular pertussis vaccines.

Bordetella pertussis, the causative agent of whooping cough, has experienced a resurgence in the past 15 years, despite the existence of both whole-cell and acellular vaccines. Here, we performed whole genome sequencing analysis of 149 clinical strains, provided by the National Institute of Infectious Diseases (NIID), Japan, isolated in 1982-2014, after Japan became the first country to adopt acellular vaccines against B. pertussis. Additionally, we sequenced 39 strains provided by the Konan Kosei Hospital in Aichi prefecture, Japan, isolated in 2008-2013. The genome sequences afforded insight into B. pertussis genome variability and population dynamics in Japan, and revealed that the B. pertussis population in Japan was characterized by two major clades that divided more than 40 years ago. The pertactin gene was disrupted in about 20 % of the 149 NIID isolates, by either a deletion within the signal sequence (ΔSS) or the insertion of IS element IS481 (prn :: IS481). Phylogeny suggests that the parent clones for these isolates originated in Japan. Divergence dating traced the first generation of the pertactin-deficient mutants in Japan to around 1990, and indicated that strains containing the alternative pertactin allele prn2 may have appeared in Japan around 1974. Molecular clock data suggested that observed fluctuations in B. pertussis population size may have coincided with changes in vaccine usage in the country. The continuing failure to eradicate the disease warrants an exploration of novel vaccine compositions.

Tumor exosomes: a double-edged sword in cancer therapy.

Tumor cells produce and secrete more nucleic acids, proteins and lipids than normal cells. These molecules are transported in the blood or around the cells in membrane-encapsulated exosomes. Tumor-derived or tumor-associated exosomes (usually 30-100 nm in diameter) contain abundant biological contents resembling those of the parent cells along with signaling messengers for intercellular communication involved in the pathogenesis, development, progression, and metastasis of cancer. As these exosomes can be detected and isolated from various body fluids, they have become attractive new biomarkers for the diagnosis and prognosis of cancer. Furthermore, tumor exosomes have also attracted increasing attention due to their potential as novel therapeutic strategies for the treatment of cancers. On the one hand, the lipid bilayer membrane-encapsulated vesicles are promising carriers of drugs and other therapeutic materials targeting specific cancer cells. On the other hand, tumor exosomes are important mediators for modulation of the microenvironment that orchestrates events critical to the growth and metastasis of cancer cells as well as chemoresistance. Here, we summarize the advances in our understanding of tumor-associated or tumor-derived exosomes in recent years, and discuss their roles in cancer development, progression, invasion, and metastasis of cancers and, more importantly, their potential in strategies for precision therapy of various cancers as well as important caveats.

Versatile effects of bacterium-released membrane vesicles on mammalian cells and infectious/inflammatory diseases.

Gram-negative bacterium-released outer-membrane vesicles (OMVs) and Gram-positive bacterium-released membrane vesicles (MVs) share significant similarities with mammalian cell-derived MVs (eg, microvesicles and exosomes) in terms of structure and their biological activities. Recent studies have revealed that bacterial OMVs/MVs could (1) interact with immune cells to regulate inflammatory responses, (2) transport virulence factors (eg, enzymes, DNA and small RNAs) to host cells and result in cell injury, (3) enhance barrier function by stimulating the expression of tight junction proteins in intestinal epithelial cells, (4) upregulate the expression of endothelial cell adhesion molecules, and (5) serve as natural nanocarriers for immunogenic antigens, enzyme support and drug delivery. In addition, OMVs/MVs can enter the systemic circulation and induce a variety of immunological and metabolic responses. This review highlights the recent advances in the understanding of OMV/MV biogenesis and their compositional remodeling. In addition, interactions between OMVs/MVs and various types of mammalian cells (ie, immune cells, epithelial cells, and endothelial cells) and their pathological/preventive effects on infectious/inflammatory diseases are summarized. Finally, methods for engineering OMVs/MVs and their therapeutic potential are discussed.

Will we have new pertussis vaccines?

Despite wide vaccination coverage with efficacious vaccines, pertussis is still not under control in any country. Two types of vaccines are available for the primary vaccination series, diphtheria/tetanus/whole-cell pertussis and diphtheria/tetanus/acellular pertussis vaccines, in addition to reduced antigen content vaccines recommended for booster vaccination. Using these vaccines, several strategies are being explored to counter the current pertussis problems, including repeated vaccination, cocoon vaccination and maternal immunization. With the exception of the latter, none have proven their effectiveness, and even maternal vaccination is not expected to ultimately control pertussis. Therefore, new pertussis vaccines are needed, and several candidates are in early pre-clinical development. They include whole-cell vaccines with low endotoxin content, outer membrane vesicles, new formulations, acellular vaccines with new adjuvants or additional antigens and live attenuated vaccines. The most advanced is the live attenuated nasal vaccine BPZE1. It provides strong protection in mice and non-human primates, is safe, even in immune compromised animals, and genetically stable after in vitro and in vivo passages. It also has interesting immunoregulatory properties without being immunosuppressive. It has successfully completed a first-in-man clinical trial, where it was found to be safe, able to transiently colonize the human respiratory tract and to induce immune responses in the colonized subjects. It is now undergoing further clinical development. As it is designed to reduce carriage and transmission of Bordetella pertussis, it may hopefully contribute to the ultimate control of pertussis.

A novel high-throughput assay to quantify the vaccine-induced inhibition of Bordetella pertussis adhesion to airway epithelia.

BACKGROUND: Pertussis or whooping cough is an acute respiratory illness caused by the Gram-negative pathogen Bordetella pertussis. Despite high vaccination coverage whooping cough is currently re-emerging in many developed countries. Although the causes of pertussis resurgence are matter of debate, emerging evidences suggest that acellular vaccines efficiently protect against the hallmark symptoms of pertussis disease but fail to prevent colonization. This presumably impacts on increased risk of bacterial transmission and consequent spread throughout the population. These evidences suggest that improved vaccines may be required for efficient bacterial clearance in the upper respiratory tract. Consequently, there is a need for novel bioassays to evaluate at pre-clinical or clinical level the impact of different vaccines on B. pertussis colonization. RESULTS: We developed a high-throughput bacterial adhesion inhibition (BAI) assay based on human respiratory cell lines and on live bacteria chemically conjugated to a fluorescent dye. Employing A549 cells as model, we evaluated the impact of antibodies elicited by acellular (aP) and whole cell (wP) vaccines on B. pertussis adhesion in vitro. Moreover, we settled the method also on polarized Calu-3 cells grown at air-liquid interface (ALI), showing that this assay can be extended to more complex cell models mimicking the airway epithelium. CONCLUSIONS: We proved that this method is a sensitive, rapid and reproducible system to evaluate the anti-adhesive properties of vaccine-induced antibodies and can be employed to assess improved pertussis vaccines.

Alternatives to HIST for acellular pertussis vaccines: progress and challenges in replacement.

The 'International Workshop on Alternatives to the Murine Histamine Sensitization Test for Acellular Pertussis Vaccines: Progress and Challenges in the Replacement of HIST' was held on 24 August 2014, in Prague, Czech Republic, as a satellite meeting to the 9th World Congress on Alternatives and Animal Use in the Life Sciences. Participants discussed the progress and challenges associated with the development, validation, and implementation of in vitro assays as replacements for the histamine sensitisation test (HIST) for acellular pertussis vaccines. Discussions focused on the consistency approach, the necessary framework for regulatory acceptance of a harmonised method, and recent international efforts towards the development of in vitro assays to replace the HIST. Workshop participants agreed that acceptable alternatives to the HIST should be based on ADP ribosylation-mediated cell intoxication and therefore that the CHO cell clustering assay, which measures cell intoxication, should be further pursued and developed as a possible replacement for the HIST. Participants also agreed to continue ongoing multinational discussions involving national and international standardisation authorities to reach consensus and to organise collaborative studies in this context for assay characterisation and calibration of reference materials.

Transferability study of CHO cell clustering assays for monitoring of pertussis toxin activity in acellular pertussis vaccines.

Current regulations for acellular pertussis (aP) vaccines require that they are tested for the presence of residual or reversion-derived pertussis toxin (PTx) activity using the mouse histamine sensitisation test (HIST). Although a CHO cell clustering assay can be used by manufacturers to verify if sufficient inactivation of the substance has occurred in-process, this assay cannot be used at present for the final product due to the presence of aluminium adjuvants which interfere with mammalian cell cultures. Recently, 2 modified CHO cell clustering assays which accommodate for the adjuvant effects have been proposed as alternatives to the HIST. These modified assays eliminate the adjuvant-induced cytotoxicity either through dilution of the vaccine (called the Direct Method) or by introducing a porous barrier between the adjuvant and the cells (the Indirect Method). Transferability and suitability of these methods for testing of products present on the European market were investigated during a collaborative study organised by the European Directorate for the Quality of Medicines & HealthCare (EDQM). Thirteen laboratories participated in this study which included 4 aP-containing vaccines spiked by addition of PTx. This study also assessed the transferability of a standardised CHO cell clustering assay protocol for use with non-adjuvanted PTx preparations. Results showed that the majority of laboratories were able to detect the PTx spike in all 4 vaccines at concentrations of 4 IU/mL or lower using the Indirect Method. This sensitivity is in the range of the theoretical sensitivity of the HIST. The Direct Method however did not show the expected results and would need additional development work.

[Acellular vaccines (DTPa/dTpa) against whooping cough, protection duration]. / Vacunas acelulares (DTPa/dTpa) contra la tos ferina: duración de la protección.

INTRODUCTION: An increase in whooping cough in most of the developed countries has been detected in the last decade. OBJECTIVE: To determine whether the administration of dTpa vaccine instead of DTPa fifth dose is contributing to the appearance of these cases. METHODS: A descriptive study based on cases of whooping cough reported during an epidemic period in the city of Alicante in the first 5 months of 2014. Only pertussis cases confirmed by PCR were included in the study, and only those vaccinated with 5 doses were included in the analysis of the period of protection. RESULTS: A total of 104 cases of pertussis confirmed by PCR were reported, with 85 cases (82%) having had 5 doses of vaccine. The mean time and standard deviation (SD) of protection was 2.1±1.1 years with dTpa, and 5.1±1.5 years with DTPa (p<.001). In the protection, adjusted for age, it was observed that, after 3 years, only 47.6% of people vaccinated with dTpa were still protected, while people vaccinated with DTPa were 100% protected (P<.001). CONCLUSIONS: This study found that people who were properly vaccinated against pertussis and received their last re-vaccination dose with dTpa had a shorter period of protection than those who were vaccinated with DTPa.

Whooping cough­where are we now? A review.

AIMS: This paper describes the recent trends of pertussis and vaccine uptake in New Zealand based on notifications and immunisation registration information since 2011. It highlights the current risk for the infant in the first months after birth and the crucial role a pertussis booster in pregnancy could play. It also aims to show that protection of infants by the acellular pertussis vaccine can be improved by timely immunisation even in a situation of improving overall uptake rates that are nearing the national target of 95%. METHODS: We analysed New Zealand notification data for pertussis, extracted from EpiSurv between August 2011 and December 2013, which included the period of the last epidemic. Pertussis immunisation coverage data were extracted from the National Immunisation Register (NIR). Population estimates were based on 2006 census data. Deprivation was analysed using the New Zealand Deprivation Index 2006. RESULTS: Despite immunisation coverage at 12 months having exceeded 90% New Zealand experienced a large epidemic from 2011 to 2014, with several hundred infant hospitalisations and three deaths. Notification data indicated an average annual rate of pertussis in the New Zealand population of 102 per 100,000 with the highest rates in the youngest age groups. While an overall increase in immunisation coverage in New Zealand was evident and the timeliness showed improvement across ethnic groups and deprivation deciles, there was a marked geographical variation within DHBs and between ethnic groups. CONCLUSIONS: Given the recent published evidence, pertussis vaccination should be offered to all mothers between weeks 28 and 38 of pregnancy. Further improvements are still possible in coverage at 6 months, particularly in Maori and but also in Pacific populations, as well as in more deprived populations. DHBs work towards achieving the 95% target can contribute to the improvement in the timeliness of immunisation.

Acellular vaccines for preventing whooping cough in children.

BACKGROUND: Routine use of whole-cell pertussis vaccines was suspended in some countries in the 1970s/1980s because of concerns about adverse effects. There was a resurgence of whooping cough. Acellular pertussis vaccines (containing purified or recombinant Bordetella pertussis antigens) were developed in the hope that they would be as effective but less reactogenic than the whole-cell vaccines. OBJECTIVES: To assess the efficacy and safety of acellular pertussis vaccines in children. SEARCH STRATEGY: We searched the Cochrane Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, issue 2) which contains the Acute Respiratory Infections Group's Specialised Register; MEDLINE (1950 to April week 2 2009) and EMBASE (1974 to April 2009). SELECTION CRITERIA: Double-blind randomised efficacy and safety trials of acellular pertussis vaccines in children up to six years old, with active follow-up of participants and laboratory verification of pertussis cases. DATA COLLECTION AND ANALYSIS: Two review authors independently performed data extraction and study quality assessment. Differences in trial design precluded pooling of the efficacy data. The safety data from individual trials were pooled using the Cochrane statistical package Review Manager 5. MAIN RESULTS: Six efficacy trials and 52 safety trials were included. The efficacy of multi-component (≥ 3) vaccines varied from 84% to 85% in preventing typical whooping cough, and from 71% to 78% in preventing mild pertussis disease. In contrast, the efficacy of one- and two-component vaccines varied from 59% to 75% against typical whooping cough, and from 13% to 54% against mild pertussis disease. Multi-component acellular vaccines is more effective than low-efficacy whole-cell vaccines, but may be less effective than the highest-efficacy whole-cell vaccines. Most systemic and local adverse events were significantly less common with acellular than with whole-cell pertussis vaccines for the primary series as well as for the booster dose. AUTHORS' CONCLUSIONS: Multi-component acellular pertussis vaccines are effective, and show less adverse effects than whole-cell pertussis vaccines for the primary series as well as for booster doses.

Effectiveness of two pertussis vaccines in preterm Danish children.

Reduced immunogenicity in preterm children has been observed for pertussis vaccines. How immunogenicity relates to clinical protection is not well-established for pertussis, and the corresponding reduction, if any, in post-licensure vaccination effectiveness among preterm children has not been determined. We conducted a nationwide cohort study of 879,424 Danish children including 1553 cases of pertussis hospitalisation. The effectiveness of pertussis vaccination, both whole-cell and acellular, was evaluated in preterm and full-term children. The effectiveness of a completed primary series of pertussis vaccination, whole-cell or acellular, was similar in preterm and full-term children.

[Pertussis: data collection and vaccinal strategy]. / La coqueluche : collecte de données et choix des stratégies vaccinales.

UNLABELLED: Renacoq is a pediatric hospital-based surveillance network in France, set up in April 1996 to monitor the trend of pertussis among children and the impact of vaccination strategies. METHOD: The authors studied the link between data collection and public health policy. Microbiologists from 43 hospitals notify diagnosis of pertussis among children less than 16 years of age. Pediatricians complete a questionnaire for infants less than 6 months of age fulfilling the case definitions. Positive cultures are sent to the National reference laboratory to validate biological results. Data collected from 1996 to 2007 was analyzed, as well as its interaction with changes in pertussis vaccine policy. RESULTS: The introduction of adolescent and adult boosters was largely supported by Renacoq data but this was not the case for interruption of whole cell vaccine use. The impact of adolescent booster is moderate because of a limited vaccine coverage. There was no observed impact of the adult booster but the coverage is very weak. The introduction and then the sole use of acellular vaccine did not have any impact on Renacoq data. DISCUSSION: The study illustrates the burden of the disease among infants and the link between surveillance data collection and public health decision. It highlights the difficulty to implement new vaccine strategies and the importance of data collection, stressing the need for a better consideration of hospital practitioners involved in public healthcare surveillance.

Avian influenza vaccines and therapies for poultry.

Vaccines have been used in avian influenza (AI) control programs to prevent, manage or eradicate AI from poultry and other birds. The best protection is produced from the humoral response against the hemagglutinin (HA) protein. A variety of vaccines have been developed and tested under experimental conditions with a few receiving licensure and field use following demonstration of purity, safety, efficacy and potency. Current licensed vaccines are predominately inactivated whole AI vaccines, typically produced from low pathogenicity (LP) AI virus strains, or occasionally from high pathogenicity AI virus strains. Recently, reverse genetic procedures have been developed that allow construction of vaccine strains using a genetically altered HA gene (changing HP HA proteolytic cleavage site to LP) and a backbone of internal gene segments for safe, high growth production. Other licensed AI vaccines include recombinant fowl poxvirus vector with an AI H5 insert and a recombinant Newcastle disease virus vector with an AI H5 gene insert. The latter vaccine can be mass administered via aerosol application.

The role of Toll-like receptor-4 in pertussis vaccine-induced immunity.

BACKGROUND: The gram-negative bacterium Bordetella pertussis is an important causative agent of pertussis, an infectious disease of the respiratory tract. After introduction of whole-cell vaccines (wP) in the 1950's, pertussis incidence has decreased significantly. Because wP were found to be reactogenic, in most developed countries they have been replaced by acellular vaccines (aP). We have previously shown a role for Toll-like receptor 4 (Tlr4) in pertussis-infected mice and the pertussis toxin (Ptx)-IgG response in wP-vaccinated children, raising the issue of the relative importance of Tlr4 in wP vaccination of mice. Here we analyze the effects of wP and aP vaccination and B. pertussis challenge, in Tlr4-deficient C3H/HeJ and wild-type C3H/HeOuJ mice. aP consists of Ptx, filamentous hemagglutinin (FHA), and pertactin (Prn). RESULTS: We show an important role of Tlr4 in wP and (to a lesser extent) aP vaccination, induction of Th1 and Th17 cells by wP but not aP vaccination, and induction of Th17 cells by infection, confirming data by Higgins et al. (J Immunol 2006, 177:7980-9). Furthermore, in Tlr4-deficient mice, compared to wild-type controls (i) after vaccination only, Ptx-IgG (that was induced by aP but not wP vaccination), FHA-IgG, and Prn-IgG levels were similar, (ii) after infection (only), lung IL-1alpha and IL-1beta expression were lower, (iii) after wP vaccination and challenge, Prn-IgG level and lung IL-5 expression were higher, while lung IL-1beta, TNF-alpha, IFN-gamma, IL-17, and IL-23 expression were lower, and lung pathology was absent, and (iv) after aP vaccination and challenge, Prn-IgG level and lung IL-5 expression were higher, while Ptx-IgG level was lower. CONCLUSION: Tlr4 does not influence the humoral response to vaccination (without challenge), plays an important role in natural immunity, wP and aP efficacy, and induction of Th1 and Th17 responses, is critical for lung pathology and enhances pro-inflammatory cytokine production after wP vaccination and challenge, and diminishes Th2 responses after both wP and aP vaccination and challenge. wP vaccination does not induce Ptx-IgG. A role for LPS in the efficacy of wP underlines the usefulness of LPS analogs to improve bacterial subunit vaccines such as aP.

WHO working group on standardisation and control of acellular pertussis vaccines--report of a meeting held on 16-17 March 2006, St. Albans, United Kingdom.

This report reflects the discussion and conclusions of a WHO group of experts from national regulatory authorities, national control laboratories, vaccine industry and other relevant institutions involved in standardisation and control of acellular pertussis vaccines, held on 16-17 March 2006, in St. Albans, UK. Following previous discussions (Bethesda, 2000; Ferney-Voltaire, 2003; Geneva, 2005) and collection of relevant data for quality control, on the one hand, and clinical evaluation of acellular pertussis vaccines, on the other, this meeting was intended to review the scientific basis for the revision of WHO guidelines adopted in 1996 [Guidelines for the production and control of the acellular pertussis component of monovalent or combined vaccines. In: WHO Expert Committee on Biological Standardisation. Forty-seventh report. Geneva, World Health Organisation, 1998 (WHO Technical Report Series, No. 878), Annex 2]. The discussion on animal protection models, immunogenicity and toxicity testing was focused on three main aspects: value of the assay for the purpose of licensing and/or lot release; validity criteria and potential optimisation of the assays. The group agreed that establishment of JNIH-3 as a potential International Standard (IS) for modified intra-cerebral challenge assay should be under consideration. It was suggested that the inclusion of a reference vaccine, such as JNIH-3 in the intra-nasal challenge model could improve the standardisation of this assay. It was proposed that the development of stable reference vaccines for immunogenicity testing should be encouraged. Further collection of the data from the countries with established lot release of acellular pertussis vaccines will be undertaken to prepare a solid basis for recommendations on toxicity tests. In the context of recommendations for clinical assessment of new vaccines, the group emphasised the importance of comparability studies with antigens that have already undergone efficacy trials in the past. The outline for the section on clinical evaluation of acellular pertussis vaccines was presented and after the consultation further additions were made. Post-marketing surveillance was recognised as an important part of overall vaccine evaluation and a unique opportunity to understand vaccine performance in the population and to establish a link with quality control.